Fluid pressure cylinder and method of manufacturing the cylinder

Abstract

A fluid pressure cylinder extends and contracts in accordance with supply/discharge of fluid pressure to/from a cylinder tube is provided. On inner side of both end portions of the cylinder tube in an axial direction, at least one small-diameter portion having a diameter smaller than those of the end portions in the axial direction is formed by a spinning process.

1 . A fluid pressure cylinder that extends and contracts in accordance with supply/discharge of fluid pressure to/from a cylindrical cylinder tube, the fluid pressure cylinder comprising:
 the cylinder tube;   a first closing member that closes one open end of the cylinder tube;   a second closing member that closes another open end of the cylinder tube;   a plurality of small-diameter portions having a diameter smaller than those of end portions in an axial direction, the plurality of the small diameter portions being formed in a middle region at inner side of both the end portions of the cylinder tube in the axial direction at prescribed intervals in the axial direction of the cylinder tube by a spinning process; and   a holding member provided on an outer circumferential surface between the plurality of the small-diameter portions formed in the middle region, the holding member being configured to hold a pipe that supplies/discharges the fluid pressure to/from the cylinder tube.   
     
     
         2 . The fluid pressure cylinder according to  claim 1 , further comprising
 supply/discharge ports welded and fixed to outer circumferential surfaces of both of the end portions in the axial direction, the supply/discharge ports being configured to supply/discharge the fluid pressure to/from the cylinder tube.   
     
     
         3 . The fluid pressure cylinder according to  claim 1 , wherein outer diameters of the plurality of the small-diameter portions provided in the middle region are the same. 
     
     
         4 . The fluid pressure cylinder according to  claim 1 , wherein outer diameters of both of the end portions in the axial direction are the same as an outer diameter of a portion in the middle region other than the small-diameter portions. 
     
     
         5 . A method of manufacturing the fluid pressure cylinder according to  claim 1 , comprising:
 fitting a mandrel inside the cylinder tube; and   performing a spinning process that reduces an outer diameter of the cylinder tube by rotating the cylinder tube, and while pressing a roller rotated thereby against an outer circumferential surface of the cylinder tube, moving the cylinder tube and the roller relative to each other in the axial direction of the cylinder tube; and   forming the plurality of the small-diameter portions in the middle region by the spinning process while performing the spinning process.